1. Field of the Invention
This invention relates to filled blends of ethylene interpolymers and more specifically it relates to filled blends of ethylene polymers plasticized with polyester, polyether and polyether ester plasticizers.
2. Description of the Prior Art
The use of plasticizers with ethylene copolymers generally is not common. Most ethylene copolymers, of which ethylene/vinyl acetate copolymers are the most widely used, are used principally to form films for packaging applications, molded parts, such as shoe soles, and extruded shapes, such as tubing. Where the benefits of plasticization such as greater flexibility, are required, the concentration of comonomer, which acts as an internal plasticizer, can be adjusted to an appropriate level. In binary blends containing fillers, physical properties typically suffer with increasing filler content: melt index decreases, resulting in higher power requirements for processing; elongation and flexibility decline, that is, the blends become more brittle; and modulus increases. These effects can be offset to some degree by changes in copolymer composition, particularly at low filler levels. However, the practical limit for addition of medium density fillers such as calcium carbonate, bauxite, gypsum, etc. is about 60% by weight. As this level is approached physical properties deteriorate to the point where the mixture is of little practical use, and it becomes difficult or impossible to prepare homogeneous blends using standard commercial methods.
Boyer U.S. Pat. No. 3,010,899 discloses blends of ethylene/vinyl acetate resin and mineral oil which are either rubbery or grease like depeneding upon the proportion of oil to resin and can be used as a substitute for crepe rubber or as a grease. It is further disclosed that fillers such as carbon black or finely divided clays can be added to the rubbery products to increase hardness and produce materials suitable as floor tile. As indicated for example in Claim 11, the filler, carbon black, is present in a "minor-amount" while the oilethylene/vinyl acetate copolymer mixture is present in a "major amount".
Nakamura et al. Japan Kokai No. 78 77, 238 discloses the use of a polyester plasticizer in filled polypropylene with other additives to improve heat resistance. In a specific example a blend consisting of 35 parts of polypropylene, 65 parts of calcium carbonate, 1.3 parts of polyester plasticizer, 0.2 parts of dimyristyl thiodipropionate, 0.1 parts of calcium stearate, and 0.05 parts of antioxidant gave heat resistance of 520 hr in a 145.degree. C. air oven compared to 230 hr for a control containing dioctyl phthalate instead of the polyester.
Taira, et al., Japanese Pat. No. 5 0151-243 discloses the use of magnesium and aluminum silicates in high density polyethylene plasticized with a polyester plasticizer to improve antistatic properties. These compositions are disclosed to contain up to 150 parts of filler and 40 parts of polyester plasticizer per 100 parts of resin.
Lamb et al., U.S. Pat. Nos. 4,085,082, 4,085,083, and 4,111,888, disclose the use of polyesters prepared from a dibasic acid, ethylene glycol, and an aliphatic alcohol, from a dibasic acid, a polyethylene glycol and an aliphatic alcohol, and from a phthalic acid, ethylene glycol, diethylene glycol or polyethylene glycol and an aliphatic alcohol, respectively, in unfilled ethylene/vinyl.sup.3 acetate copolymers containing at least 55% vinyl acetate. The plasticized compositions provided improved film clarity and improved extractability.
Larsen in "Action of Additives on High Molecular Weight Polyethylene" (Nuova Chim. 1972, 48(12), 29-32) describes the use of plasticizers in blends containing high molecular weight polyethylene and inert clay fillers to modify processing characteristics without significantly affecting physical properties. Polyester plasticizers were one of the types of plasticizers mentioned.
Schumacher and Yllo U.S. Pat. No. 4,191,798 discloses the use of processing oils, particularly naphthenic and aromatic oils, in blends of ethylene interpolymers and fillers. Specifically, the inclusion of a processing oil in blends of ethylene copolymers and fillers allows the preparation of higher filler level containing blends that can be attained in corresponding binary polymer/filler blends.
In the "Handbook of Adhesives" second edition, edited by Irving Skeist, published by the Van Nostrand, Reinhold Company in 1977, Chapter 30 written by J. T. Domine and R. H. Schaufelderg in a review of hot melt compositions it is disclosed that plasticizers or liquid modifiers are used to a limited extent in order to impart properties such as flexibility, specific wetting and viscosity characteristics to ethylene copolymer based hot melt compositions. The liquid plasticizers proposed for such use generally speaking belong to the class of organic esters, however, other liquid substances, for example, chlorinated polynuclear aromatic compounds have also been suggested. The particular plasticizer and the proportion thereof employed in a given composition depends upon several factors. Important considerations are the cost and compatibility of the plasticizer with the other ingredients of the composition, particularly with the ethylene copolymer.
Polyethers and polyether esters are commonly used as surface active agents in combination with ethylene copolymers. For example, Japanese Patent Publication No. 099-730/74, (Japanese Patent Appln. No. 012058/73) discloses the use of up to 15% of polyethylene glycol sorbitol ester or ether ester surfactant added to unfilled ethylene/vinyl acetate based hot melt adhesive formulations making such formulations water soluble.
U.S. Pat. No. 3,492,258, discloses the use of poly(oxyalkylene) glycol mono-fatty acid esters as release agents in wax coatings containing ethylene/vinyl acetate copolymers. These release agents migrate to the surface of the coating and thus impart strippability to the wax coatings. There is no filler used in these compositions.
U.S. Pat. No. 3,927,244 discloses a blend of a polyglycol terephthalate and an ethylene/vinyl acetate copolymer as a heat-bondable coating on a polyester film. The polyglycol terephthalate, which is present at a level ranging from 60 to 99.9 wt. % in this blend, is a condensation product of a polyglycol, such as polyethylene glycol, with a degree of polymerization ranging from 10 to 100, and terephthalic acid; the degree of polymerization of the copolymer of the polyglycol and terephthalic acid ranges from 10 to 500. The function of the polyglycol terephthalate in this blend is to provide adhesion to the polyester film substrate; the ethylene/vinyl acetate acts as a toughening agent where such coatings must survive impact or other abuse. The addition of fillers such as dyes, organic or inorganic pigments, and metal powders, at levels ranging up to 200 parts per hundred based on the polymer blend, is also claimed.
U.S. Pat. No. 3,361,702, discloses polyethylene glycol, polypropylene glycol, and adducts of propylene oxide with glycerol and sorbitol, for example, as plasticizers in unfilled compositions of ethylene/acrylic acid and ethylene/methacrylic acid copolymers, containing less than 25% by weight of the acid or monomer, and their sodium salts.
British Pat. No. 940,713 discloses the use of polyethers and polyether esters with ethylene/vinyl acetate copolymers primarily for but not limited to, vulcanized compounds. The polyethers described are homopolymers of ethylene oxide, propylene oxide, or butylene oxide. The use of fillers is disclosed, silicic acid and carbon black being mentioned in particular. Although specific concentrations are not discussed, it is stated that fillers can be used in very large amounts. The highest filler concentration disclosed in the examples of this patent was 30 parts filler per 100 parts of ethylene copolymer in a crosslinked composition, containing other ingredients as well (i.e., about 22-23% filler based upon the weight of the filled composition).
U.S. Pat. No. 4,242,395 discloses thermoplastic compositions which are useful as backings for automotive carpets. These compositions comprise at least 60 percent by weight of inert mineral filler, 5 to 25 percent by weight of an ethylene homopolymer or copolymer (e.g. ethylene/vinyl acetate, ethylene/ethyl acrylate), 1 to 10 percent by weight of a nonvulcanized elastomeric resin, and 1 to 15 percent by weight of a plasticizer. The plasticizers disclosed include oils employed in rubber compounds and plasticizers commonly used with polyvinyl chloride. Of the latter type phthalates, terephthalates and epoxidized oils were mentioned specifically. The relatively low molecular weight, liquid plasticizers were indicated to be preferred. Apparently the preferred hydrocarbon oils and polyvinyl chloride plasticizers give equivalent property performance. No specific mention is made of polyesters, or of polyethers, or their mixtures with hydrocarbon oils, as plasticizers. It is disclosed that part or all of the ethylene copolymer can be replaced with polyethylene.